Bottom hole assembly comprising flow through setting tool and frac plug

ABSTRACT

A bottom hole assembly comprising a hydraulic setting tool, a frac plug, and usually also an adapter for connecting the frac plug to the setting tool. The setting tool, adapter, and frac plug, all include continuous flow passages that allow fluid to be circulated in the well ahead of the plug as the bottom hole assembly is advanced. This removes debris present in the well and prevents the frac plug from becoming lodged in the well in other than the desired location. The setting tool includes a bypass feature that signals reliably when the plug has been successfully deployed. The bypass assembly comprises sliding members with bypass ports that can become aligned only when the collar on the frac plug has advanced far enough to ensure complete deployment of the frac plug.

FIELD OF THE INVENTION

The present invention relates generally to setting frac plugs in oil andgas wells.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a bottom hole assembly constructedin accordance with the present invention.

FIG. 2 is a longitudinal, partly sectional view of a conventional fracplug connected to an adapter with a flow passage made in accordance withthe present invention.

FIG. 3 is a longitudinal sectional view of a setting tool and adaptermade in accordance with the present invention. The tool is shown in theretracted or neutral position.

FIG. 4 is a longitudinal sectional view of the setting tool and adaptershown in FIG. 3 illustrating the extended position used to deploy thefrac plug.

FIGS. 5A-5D show an enlarged, longitudinal sectional view of the settingtool and adapter shown in FIG. 3.

FIGS. 6A-6D show an enlarged, longitudinal sectional view of the settingtool and adapter shown in FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Frac and bridge plugs are used to isolate zones in a well. Plugstypically are placed in position using a setting tool, such as ahydraulic setting tool. The frac plug is attached to the setting toolwhich is then run downhole on coiled tubing, jointed pipe or otherconduit. It is not unusual to encounter debris as the plug is advanceddown the well. This debris tends to collect ahead of the bottom holeassembly (“BHA”) and may slow or even block proper positioning of theplug.

Some frac plugs have a flow passage that allows fluid to pass up throughthe plug from the well below after the plug is set. The presentinvention takes advantage of this flow passage by employing a hydraulicsetting tool with a flow passage to provide fluid communication throughthe entire BHA as the plug is being advanced. Thus, fluid can becirculated through the well to wash away debris as the plug is advancedto the selected location in the well.

Setting tools are used to set a variety of plugs and packing devices.One difficulty associated with setting such devices is determining whenand if the plug or device has been completely and successfully deployed.The setting tool of the present invention incorporates a fluid bypasssystem that reliably indicates successful deployment of the plug orother device by producing a precipitous drop in the hydraulic pressure.This is accomplished by using a system of fluid bypass ports that becomealigned only when the sliding component of the setting tool has traveleda distance sufficient to completely set the plug.

Turning now to the drawings in general and to FIG. 1 in particular,there is shown therein a bottom hole assembly constructed in accordancewith a preferred embodiment of the present invention and designatedgenerally by the reference numeral 10. As used herein, “bottom holeassembly” or “BHA” refers to a combination of tool members connected tothe end of coiled tubing, string of pipe joints, or other well conduitfor performing one or more operations downhole.

The BHA 10 shown in FIG. 1 is adapted for connection to coiled tubing(not shown) and therefore the uppermost component is a coiled tubingconnector 12. Next is a flapper valve 14, hydraulic disconnect 16,eccentric weight bar or sub 20, and an oriented perforator 22. Beneaththe oriented perforator 22 is a hydraulic setting tool 30 and an adapter32, both made in accordance with the present invention, as well beexplained below. Finally, connected to the adapter 32 is a conventionalfrac plug 34 of the type that has a flow passage through it. It will beunderstood that this BHA 10 is only an example of the type of tools andcomponents that may be combined in a BHA. The number and type of toolsand connectors will vary widely depending on the well and the nature ofthe operations to be performed.

The adapter 32 and frac plug 34 are shown in more detail in FIG. 2. Thefrac plug 34 generally comprises rubber packer elements 40 mounted on aplug mandrel 42 between slips 44 a and 44 b. In a known manner, when theslips 44 a and 44 b are moved closer together by force on an upper ringor collar 46, the packer elements 40 are squeezed outwardly until theyfrictionally engage in the side of the well casing (not shown). The plugmandrel 42 is tubular defining a flow passage 48 extending the length ofthe plug and exiting the lower, open end 38.

The adapter 32 comprises an inner tension mandrel 50 and an outer sleeve52. The uphole end 54 of the sleeve 52 is threaded for connection to thesetting tool 30, as will be described in more detail hereafter. Thetension mandrel 50 is tubular with a wider lower portion 56 and anarrower upper portion 58. The upper portion 58 has a threaded end 60for connection to the setting tool 30 as described further below. Thelower portion 56 is sized to slidingly receive the upper end 62 of theplug mandrel 42 and is connected thereto by at least one and preferablya plurality of shear pins or screws, designated collectively at 64. Byway of example only, the shear screws 64 may comprise 5 shear screws,each having a maximum shear strength of 5000 pounds so that 30,000pounds of force is required to break them and release the frac plug. Theinner bore or lumen 66 of the tension mandrel 50 forms a flow passagetherethrough continuous with the flow passage 48 in the plug 34.

It should be noted that an adapter is not essential to the presentinvention. Rather, in some instances a setting tool may be designed tobe connected directly to the frac plug (or other device). That is, thecomponents required to connect the setting tool to the frac plug may beincorporated in the setting tool. However, as is well known in the art,the use of an adaptor permits a particular setting tool to be used withmultiple sizes and types or plugs.

The preferred setting tool 30 connected to the adapter assembly 32 isshown in FIGS. 3 and 4 and also FIGS. 5A-5D and 6A-6D. FIGS. 3 and 5A-5Dshow the setting tool 30 in the retracted or undeployed position. FIGS.4 and 6A-6D show the setting tool 30 in the extended or deployedposition. The setting tool 30 comprises an upper housing assembly 70, amandrel assembly 72, and a slide assembly 74.

The upper housing assembly 70 preferably comprises a top sub 76 with anuphole end 78 threadedly connectable to the well conduit (not shown) orto another BHA component, such as the oriented perforating tool 22 (FIG.1). The upper housing assembly 70 also preferably comprises an upperhousing 80, the uphole end 82 of which is connected to the downhole end84 of the top sub 76 by a set screw 86 (FIGS. 5A & 6A).

In the preferred embodiment, the mandrel assembly 72 comprises aplurality of tubular components all axially fixed relative to the upperhousing assembly 70. An elongated tubular piston mandrel 90 is connectedat is uphole end 92 to the downhole end 84 of the top sub 76. The pistonmandrel 90 is threadedly connected at its downhole end 94 to the upholeend 96 of a circulating sub 98 (FIGS. 5C & 6C). As best seen in FIGS. 3and 4, the lumen 100 of the mandrel 90 forms a flow passage that extendsthe length of the mandrel and connects to the flow passage 102 extendingthrough the top sub 76.

As best seen in FIGS. 5C and 6C, the downhole end 104 of the circulatingsub 98 is threadedly connected to the uphole end 106 of a bottom sub108. The downhole end 110 of the bottom sub 108 is threadedly connectedto the uphole end 60 of the tension mandrel 50. A flow passage 112extends the length of the circulating sub 98, and a flow passage 114extends the length of the bottom sub 108. The flow passage 112 in thecirculating sub 98 defines a ball seat 116 (FIG. 5C) to receive a ball118 (FIGS. 3, 4 and 6C), for a purpose yet to be described.

Referring still to FIGS. 3, 4, 5A-5D, and 6A-6D, the slide assembly 74comprises an upper piston 120 with an annular head 122, a lower end 124and a tubular body 126 therebetween. The lower end 124 (FIG. 5B) isthreadedly connected to the upper end 128 of a push sleeve 130. Thelower end 132 of the push sleeve 130 is connected to the upper end 54 ofthe adapter sleeve 52 (FIGS. 5C & 6C). As seen in FIGS. 5B & 6C, thepiston body 126 is temporarily fixed against axial movement relative tothe upper housing assembly 70 by one or more shear screws 134. A lowerpiston 136 is carried on the upper end 128 of the push sleeve 130, beingcaptured by a shoulder 138 in the inner sidewall of the piston body 126.

As best shown in FIGS. 5C and 6C, the setting tool 30 further comprisesa bypass assembly 140. The bypass assembly 140 comprises a bypass sleeve142 slidably supported on the circulation sub 98. The bypass sleeve 142is temporarily fixed against axial movement relative to the circulationsub 98 by means of shear screws or pins 144.

A plurality of ports 150 are formed in the bypass sleeve 142. Ports 152are also formed in the circulation sub 98. Ports 154 are formed in thepush sleeve 130. The ports 150, 152, and 154 are sized and positioned tobe alignable with each other when the slide assembly 74 is moved axiallya selected distance “D” (FIG. 4) on the piston mandrel 90. The alignmentof the ports then forms a continuous flow path from the lumen 100 insidethe tubular piston mandrel 90 through the sides of the circulation sub98, the bypass sleeve 142, and the push sleeve 130, as will be explainedmore fully below.

The above-described components of the setting tool 30 are configured toprovide a hydraulic system 160 for driving axial movement of the slideassembly 74. The preferred configuration for the hydraulic system 160includes an upper fluid chamber 170, which contains the head 122 of theupper piston 120, and a lower fluid chamber 172, which contains thelower piston 136. The piston mandrel 90 includes an annular flange 174along its length to form a divider between the upper and lower chambers170 and 172. As seen in FIGS. 5B and 6B, the upper face of the flange174 forms an inclined shoulder 176 that engages a complimentary lowerface 178 on the piston head 122.

The upper chamber 170 (FIGS. 6A & 6B) is defined by the inner diameterof the upper housing 80 and the outer diameter of the piston mandrel 90above the annular flange 174 of the piston mandrel 90. O-rings(unnumbered) seal the upper chamber 170 between the upper end 82 of theupper housing 80 and the lower end 84 of the top sub 76. Similarly,O-rings (unnumbered) seal the interface between the piston head 122 andthe upper end 82 of the upper housing 80 and between the annular flange174 and the lower end 124 of the upper piston 120. Ports 182 near theupper end 92 of the piston mandrel 90 provide fluid communicationbetween the lumen 100 of the piston mandrel and the upper fluid chamber170 (FIGS. 5A and 6A).

The lower chamber 172 is defined by the inner diameter of the upperpiston body 126 and the outer diameter of the piston mandrel 90 belowthe annular flange 174. Ports 186 (FIGS. 5B & 6B) in the piston mandrel90 below the annual flange 174 provide fluid communication between thelumen 100 of the piston mandrel 90 and the lower fluid chamber 172.

Having described the structure of the preferred BHA 10, its operationnow will be described with continued reference to FIGS. 3, 4, 5A-5D, and6A-6D. First, the frac plug 34 is positioned at the selected level inthe well (not shown). As the plug is advanced down the well, fluid ispumped through the BHA 10 to flush the well ahead of the plug 34 toprevent debris or other matter in the well from obstructing the properplacement of the plug. Now it will be understood that the flow passages102, 100, 112, and 108 all provide a continuous flow path through theBHA 10 so that fluid exiting the open end 38 of the frac plug 34 (FIG.2) flushes debris.

Once the plug 34 is positioned at the correct level, a ball 118 (FIGS.5A & 6C) is pumped down conduit to the BHA. When the ball 118 is seatedin the ball seat 116, fluid flow through the circulation sub 98, bottomsub 108, adapter 32, and frac plug 34 stops. Consequently, pressurebegins to build inside the piston mandrel 90, forcing fluid to flowthrough the ports 182 and 186 in the upper and lower fluid chambers 170and 172. This exerts force on the head 122 of the upper piston 120 andon the lower piston 136, breaking the shear pins 134 between the upperhousing 80 and the upper piston 120. These may be relatively weak pins,preferably having a maximum shear strength of only about 1000 pounds.The primary purpose of these pins is to keep the slide assembly 74 fromdeploying partially as the BHA is run downhole.

Once the shear pins 134 have broken, the slide assembly 74 movesdownward in response to the force on the piston head 122 and the lowerpiston 136. After several inches of travel, the frac plug 34 will befully deployed. In most instances, 4-5 inches of travel will besufficient to set the plug 34.

The slide assembly 74 continues to move downwardly until the lowerpiston 136 engages the upper end of the bypass sleeve 142. The force onthe sleeve 142 increases until sufficient to break the shear pins 144,whereupon the slide assembly 74 completes its full travel distance “D”(FIG. 4). In this position, the ports 152 in the circulation sub 98 andthe ports 150 in the bypass sleeve 142 are aligned with the ports 154 inthe push sleeve 130.

The aligned ports 150, 152, and 154 allow a sudden increase in the flowof fluid out of the tool, causing a dramatic drop in the pressurereading at the wellhead (not shown). As used herein, “rapid andsubstantial pressure drop” refers to a pressure drop that is sudden andlarge enough to be readily perceived by the well operator and sufficientto signal to the operator that the setting operation is completed. Byway of example only, in the preferred setting tool, alignment of theports should produce at least about a 2000 psi pressure drop in a boutfifteen seconds.

Having successfully deployed the frac plug 34, the frac plug isdisengaged from the BHA. Continued pressure from the hydraulic systembreaks the shear pins 64 between the tension mandrel 50 in the adapter32 and the plug mandrel 42, releasing the connection between the BHA andthe plug 34. Thereafter, the BHA may be withdrawn from the well.

For the purpose of this description, the words left, right, front, rear,top, upper, lower, inward, outward, uphole, downhole, bottom, up,upwardly, down, downwardly, inside, and outside may be used to describethe various parts and relative positions of structures and operations inthe present invention as depicted in the drawings. These descriptiveterms should not be considered as limiting the possible orientations ofthe invention or how it may be used.

Now it will be appreciated that the present invention provides frac plugsetting tools and methods that offer many advantages. The bottom holeassembly provides a “flow through” function that allows fluid to becirculated through the well ahead of the frac plug as it is beingadvanced toward the desired location. The setting tool includes a bypassfeature that is mechanically simple and reliably signals the successfuldeployment of the plug. As regards the setting tool, it should be notedthat a setting tool with this bypass function is useful in operationsother than setting frac plugs and with or without the “flow through”feature.

The embodiments shown and described above are exemplary. Many detailsare often found in the art and, therefore, many such details are neithershown nor described herein. It is not claimed that all of the details,parts, elements, or steps described and shown were invented herein. Eventhough numerous characteristics and advantages of the present inventionshave been described in the drawings and accompanying text, thedescription is illustrative only. Changes may be made in the details,especially in matters of shape, size, and arrangement of the partswithin the principles of the inventions to the full extent indicated bythe broad meaning of the terms of the attached claims. The descriptionand drawings of the specific embodiments herein do not point out what aninfringement of this patent would be, but rather provide an example ofhow to use and make the invention. Likewise, the abstract is neitherintended to define the invention, which is measured by the claims, noris it intended to be limiting as to the scope of the invention in anyway. Rather, the limits of the invention and the bounds of the patentprotection are measured by and defined in the following claims.

1. A bottom hole assembly for connection to the end of a well conduithaving a fluid flow passage therethrough, the assembly comprising: afrac plug having a downhole end and an uphole end and a flow passageextending therebetween for passing fluid through the plug; a hydraulicsetting tool having a downhole end and an uphole end and a flow passageextending therebetween for passing fluid through the tool; wherein theuphole end of the frac plug is connected to the downhole end of thesetting tool so that the flow passage in the setting tool is in fluidcommunication with the flow passage in the frac plug.
 2. The bottom holeassembly of claim 1 further comprising an adapter for connecting thesetting tool to the frac plug, wherein the adapter comprises a flowpassage for passing fluid through the adapter.
 3. A method for setting afrac plug, comprising: flowing fluid through the frac plug as it isadvanced down the well.
 4. A setting tool for use with a well conduit toactivate a downhole tool, the downhole tool comprising a stationarymember and a sliding member, the setting tool comprising: an upperhousing assembly having an upper end, the upper end being connectable toa well conduit; a piston mandrel assembly with an upper end connectableto the upper housing assembly and a lower end connectable to thestationary member of the downhole tool so as to prevent axial movementtherebetween; a slide assembly comprising a sleeve engageable with thesliding member of the downhole tool and slidably supported on the pistonmandrel for movement relative thereto along a selected range of travelfrom a retracted position to an extended position, wherein the range oftravel is sufficient to activate the downhole tool; a hydraulic systemconfigured to drive the movement of the slide assembly to complete therange of travel; a bypass assembly comprising a plurality of portsmovable between aligned and non-aligned positions, wherein in thealigned positions, the ports allow release of hydraulic fluid from thehydraulic system sufficient to produce a rapid and substantial pressuredrop, wherein the bypass assembly is configured to align the ports whenthe sleeve in the slide assembly has completed the selected range oftravel.
 5. The setting tool of claim 4 wherein the setting tool ischaracterized by a flow passage extending therethrough and wherein thedownhole tool is a frac plug with a flow passage extending therethroughthat is continuous with the flow passage in the setting tool and withthe conduit.